Pneumatic positioning table



April 1968 R. SCHARDT 3,376,764 I PNEUMATIC POSITIONING TABLE Filed Aug.19, 1965 3 Sheets-Sheet 1 34 RUDOLF SCHARDT KJ -Pd J 1N VENTOR.

A ril 9, 1968 R. SCHARDT 3,376,764

PNEUMATIC POSITIONING TABLE Filed Aug. l9, 1965 3 Sheets-Sheet 2 F' 1,us ue I06 IOGA lo 2&

R UDOLF S CHARDT INVENTOR.

R. SCHARDT April 9, 1968 3 Sheets-Sheet 5 Filed Aug. 19, 1965 RUDOLFSCHARDT INVENTOR United States Patent 3,376,764 PNEUMATIC POSITIONINGTABLE Rudolf Schardt, 3510 Laverne Drive, Houston, Tex. 77024Continuation-impart of application Ser. No. 230,353, Oct. 15, 1962. Thisapplication Aug. 19, 1965, Ser. No. 480,965 The portion of the term ofOct. 5, 1982, has been to the Public 5 Claims. (Cl. 77--64) Thisapplication is a continuation-in-part of my copending application Ser.No. 230,353, filed Oct. 15, 1962, and now Patent No. 3,209,263.

This invention pertains generally to machine tools, and particularly topositioning devices which may be used as components of machine tools.

In the machine tool art, particularly in machine shops, drill jigs whichare used to accurately locate and guide a drill or similar cutting toolon a work piece for the purpose of material removal present a costly andtime-consuming problem. Such jigs require precision in the constructionof component parts, and, therefore, highly skilled personnel arerequired for constructing and maintaining the jigs in operablecondition. For many years improved methods and means for rapidly andinexpensively indexing or positioning work pieces with relation to thecutting tool have been elusive problems.

Also in known positionin devices time-consuming effort has been requiredfor locking the jigs to properly position the work piece relative to thecutting tool. Conventional positioning devices commonly requireguideways, such as Vs or dovetails of various shapes to form abutmentsagainst which the positioning device or jig is secured to properlyposition the work piece. Such abutment means, however, necessarily limitthe freedom of movement of the positioning relative to the cutting tool,generally to two directions and thus greatly reduce the efficiency ofthe machining operations. Furthermore, known locking apparatus has leftmuch to be desired in the way of simplicity, low cost, reliability, andlack of distortion due to locking forces.

In the aforesaid copending application, I have disclosed a novel form ofpositioning device for positioning a work piece by the employment of apositioning table which is frictionlessly supportable on an air film orso-called air bearing forfree movement relative to an indexing templateand which employs vacuum means for locking the positioning device inplace when the work piece has been appropriately positioned.

One of the features of my invention is the ability to move a positioningtable with complete freedom as to direction so that it is possible toaccurately position a work piece without the use of the conventionalguide ribs or flanges which, as noted, necessarily limit the directionof movement of the work-supporting table with respect to the base.

My aforesaid copending application also disclosed the use of apantograph arrangement for coupling the movable work table to a base soas to keep the XY axes of the work table with respect to the base trueat all times the patent subsequent to disclaimed and dedicated a drawingor a device which I are employed the application of vacuum in lockingthe so that irrespective of the direction of movement of thework-supporting table relative to the base these axes will be kept trueand thereby assure absolutely accurate indexing of the work with respectto the cutting tool. By combining the pantograph element with the airbearing and vacuum lock arrangement, the operator has complete freedomin the direction of movement of the work-supporting table relative tothe indexing elements. It should be understood that the employment ofthe pantograph means in this connection is altogether different than thecommon application of a pantograph, which is ordinarily positioningdevice to the base may tend to suck some of the liquid between thebearing surfaces of the positioning table and base and thence into thevacuum pump and create difliculty in operation. The present inventionhas for one of its objects the provision of an improved positioningtable employing means which will be effective to prevent such liquidsfrom being drawn into the vacuum pump and will, therefore, overcome thedifiiculty noted.

Accordingly, it is a principal object of the present invention toprovide the improved work-positioning apparatus.

An important object is the provision of a work-positioning apparatusemploying an air-bearing for floating the positioning table to permitmovement thereof relative to a base of like support, and vacuum meansfor locking the positioning device to the base.

A further object is the provision of a positioning device employingvacuum locking means and which includes airoperated shield means forpreventing entrance of cooling fluid into the vacuum-applying means.

Still another object of the present invention is to provide apositioning apparatus in which a movable positioning table is coupled toa supporting base by a pantograph device which accurately andcontinuously maintains the X-Y axes of the positioning device to thesupporting base completely true throughout all movements of thepositioning device.

Other and more specific objects and advantages of this invention willbecome more readily apparent from the following detailed descriptionwhen read in conjunction with the accompanying drawings which illustrateseveral useful embodiments in accordance with this invention.

In the drawings:

FIG. 1 is a cross-sectional, elevational view partly schematic, of theinvention showing the positioning table 'in locked condition;

FIG. 2 is a cross-sectional, elevational view of a portion of thepositioning table shown in FIG. 1 when the locking means is in unlockedcondition;

FIG. 3 is a plan view taken along line 3-3 of FIG. 2;

FIG. 4 is a plan view showing a pantograph and a microscope attachmentincorporated in the present invention;

FIG. 5 is an elevational view of the pantograph and microscopeattachment shown in FIG. 4;

FIG. 6 is a side elevational view of one of the pantograph arms; and

FIGS. 7 to 11, inclusive, are fragmentary, sectional views showingseveral different modifications of shield means by which cutting fluidsor the like may be excluded from entrance between the positioning tableand its supporting base.

In practicing the invention, one embodiment of suitable positioningapparatus is provided for positioning a work piece in relation to a tooland then locking the work piece after the selected positioning hasoccurred. The positioning and locking means of the present invention mayinclude a base, a work table, an indexing plunger, a template, a sourceof compressed air and controls therefor, and a controlled vacum. Thebase provides a flat top surface and an indexing plunger assembly may besuitably located in the base. The indexing plunger may be spring-loadedso that it projects above the base surface and is connected to adiaphragm assembly inside the base. The projecting portion of theplunger may be tapered or of other suitable shape for ease inregistering with the holes in the template. An air inlet in thediaphragm chamber enables air pressure to retract the plunger below thebase surface to free the table for movement to another point relative tothe template. When the air pressure is removed from the diaphragmchamber, the spring will return the plunger against the templatesurface. The work table then is moved until the plunger projects intoanother hole in the template. A plurality of air holes are locatedaround the plunger and it is through these holes that low air pressureis supplied below the work table for the purpose of floating the worktable on a film of air. The air pressure may be adjustable, since therequired pressure depends on the work piece weight and area of the worktable. The template may be carried in a recess under the work table andthe hole pattern required on the work piece will be laid out on thetemplate. Holes of proper size are provided in the template so that thespring-loaded plunger may register without any play, thereby locatingthe work table with the work piece accurately for each operation. Oncethe work table is located, a vacuum may be drawn under the work table tosecure the table against any shifting during the working operation. Incertain instances vacuum may not be necessary when the torque created bythe working tool on the work piece is relatively small.

An alternate arrangement of the present invention utilizes a pantographand microscope attachment whereby the template may be eliminated byworking off of an accurate drawing. When the pantograph and microscopeattachment is used, a drawing table is fastened to the base.

A pantograph connects the work table to the base. A support on the worktable receives a microscope of the desired power with a crosshairreticle. The hole centers on the drawing are sighted through themicroscope and the work table is properly positioned and vacuum lockedprior to the operation on the work piece.

It is important to understand, however, that the pantograph coupling themovable work table to the base may be employed without a guiding device,such as the microscope, but may also be employed with indexing plungersas herein described, or any other indexing arrangement, it beingparticularly important in an apparatus of the type herein described,wherein a working-supporting table is to be moved on an air filmrelative to a cutting tool and an indexing arrangement, to employ thepantograph coupling, herein disclosed, between the work table and thebase to effect absolutely accurate positioning of the work table withoutlimiting the freedom in direction of movement in positioning the work.

Referring now to the drawing in detail, FIG. 1 is a combined schematicand cross-sectional, elevational view of one embodiment of the presentinvention. A base member, designated generally by the numeral 10, has afiat planar upper surface 1011. A work-supporting table 11 is disposedfor movement over surface a and is formed with a lower face 11a which isalso of generally fiat planar form adapted to seat snugly on surface 10awhen the table is in locked position, as will be described subsequently.Base member 10 has two openings 12 and 14. Through opening 12 gaspressure provides control of the indexing plunger through a diaphragm42. Opening 14 offers access to the chamber provided by a cavity 18 inlower table face 11a when table 11 rests on surface 10a. A gas pressuresource 20 connects to a multi-port plunger control valve 26 and a lowerpressure air tank 28, respectively. The gas pressure source may be apneumatic source, such as the shop air supply found in most machineshops.

The low pressure air tank 28 is coupled to a multi-port valve 30 whichcontrols the floating and locking of the work table. Also coupled tovalve 30 is a vacuum tank 32 which is coupled to a vacuum pump (notshown) through a vacuum inlet 34. An actuator 36 is coupled to controlvalve 26 and to the table float and lock valve 30. The actuator may be afoot pedal or other suitable apparatus which is convenient for theparticular operation being performed.

The central portion of base It) includes indexing plunger means. Thelatter includes resilient means 38, plunger 40, and diaphragm 42.Resilient means 38 may be a spring suitably coupled to a portion of thebase and to one end 44 of plunger 40. Diaphragm 42 is disposedintermediate the resilient means 38 and is also coupled to end 44 ofplunger 40. The opposite end 41 of plunger 40 is tapered to fit into aplurality of locating holes, such as holes 43 and 45, provided in atemplate 46. Template 46 is positioned in recess 18 of work table 11.The latter has a work piece W positioned thereon for machining by asuitable tool, such as a drill 54, to provide holes, such as holes 56and 58, in the work piece.

FIG. 1 shows the work piece W in position for tool 54 to penetrate thework piece which has been aligned by the plunger 46 through engagementin the appropriate hole in template 46. FIG. 1 shows the work table in alocked position which has been created by the application of a vacuumbetween face 11a of work table 11 and surface 10a of base 10.

FIG. 2 shows a portion of the base and table assembly of FIG. 1 with thework table 11 in a floating position. To attain this floating position,gas pressure will have been applied through inlet 12 above diaphragm 42to cause the latter to move downwardly and overcome the force ofresilient means 38. The downward movement of diaphragm 42 causes plunger40 to be retracted so that the tapered end 41 will be withdrawn fromengagement with template 46. Simultaneously, low pressure air is causedto enter recess 18 through inlet 14. The air will escape through space60 between work table face 11a and surface 10a of base 10. Thus, whenair pressure is applied to the apparatus of the present invention, alifting action occurs on the work table which will then float on thefilm of air interposed between the work table and base, so that the worktable is freed to be moved relative to the base in a frictionlessmanner. The amount of pressure necessary for raising the work table fromthe base will be dictated, as will be evident, by the Weight of the workpiece W and the contact area of work table 50.

As best seen in FIG. 3, a plurality of ports, such as ports 62 and 64,allow communication between chamber 18 and the low pressure air sourceor vacuum source, depending upon the position of valve 30.

Thus, actuator 36, shown in FIG. 1, provides control of the gas pressureapplied to diaphragm chamber 16 and to chamber 18 to float the worktable 11 relative to base 10. Actuator 36 has three operating positions:At full actuation valves 26 and 30 are operated; valve 26 actuatesdiaphragm 42, thereby retracting plunger 40; simultaneously, valve 39supplies chamber 18 with low pressure, lifting work table 1 1 andpermitting it to be slid on an air film over the upper surface 10a ofbase 10. At intermediate actuation of actuator 36, diaphragm pressurewill be exhausted to atmosphere and plunger 40 will project intoengagement with the under face of template 46 due to the biasing forceexerted by spring 38 and will, upon lateral movement of the work table,project into another locating hole provided in template 46. Due to lowfriction of the pneumatic bearing provided by escaping air at the underface 11a of work table 11 and the upper surface 16a of base 10, plunger40 will locate table 11 with ease and great accuracy. After properlocation is thus obtained, actuator 36 is returned to a basic positionwhere valve 30 has switched from low pressure gas supply to vacuumsupply, the application of the vacuum thus locking the work table firmlyto the base.

From the foregoing, it will be noted that with the arrangementdescribed, there are no restrictions upon the free movement of the worktable with respect to the base in order to move the template in relationto the indexing plunger for purposes of indexing the work piece toanother position with respect to the cutting tool. It will be noted thatno conventional guideways, flanges, or buttressing elements of any sortare employed to con- 1'5 trol or limit the direction of movement of thework table.

In order, however, to assure complete accuracy in aligning the work withthe cutting tool, the present invention employs a pantograph arrangementfor coupling the work table to the base. Such a pantograph arrangementis illustrated in FIGS. 4 to 6, inclusive. As seen in FIG. 4, thepantograph, designated generally by the numeral 100, comprises a pivotring 102, a pair of upper spaced-apart parallel arms 102103, having oneend pivotally connected at diametrically spaced points to the upper faceof ring 102 by pivot pins 104104, and having their opposite endspivotally connected to an extension 111 of table 11 by means of pivotpins 105-105. The second pair of parallel arms -6-106 are similarlypivotally secured at one end at diametrically spaced points to the lowerface of ring 102 by means of pivots 107107 oriented at 90 with respectto pivots 104- 104. The opposite ends of parallel arms .106 arepivotally secured by means of pivot pins 108-108 to a bracket arm 109securely mounted to base 10. As will be evident from the arrangementillustrated in FIG. 4, the coupling provided by the pantogr-aph betweenwork table 11 and base 10 necessarily forces all movements of work table11 to maintain the XY axes of the work table parallel at all times tothe X-Y axes of the base. Thus, the work table may be moved in anydirection required to register a template hole with the indexing plungerwhile maintaining complete accuracy in locating the work relative to thecutting tool.

Since the work table must be elevated with respect to the base duringmovement from place to place on the air bearing, one or both pairs ofarms 103 and 106 is constructed of a resilient, metallic material, sothat sufficient bending of the arms out of the planes thereof may occurto accommodate the elevation of the work table when it is raised fromthe base by the air. As illustrated, arms 103 and 106 includeintermediate sections 103a and 106a, respectively, constructed of aflexible material suitable to accomplish this desired function. Theflexibility of the arms will not interfere with the freedom of movementof the work table, but will, as noted, allow the table to be elevateduniformly and thereby avoid any binding due to creation of the airbearing under the work table.

As illustrated also in FIGS. 4 and 5, guidance of the work table inindexing the work relative to the cutting tool may be effected by meansof a microscope '122 shown mounted on an arm 124 secured to a side ofthe work table opposite the points of connection of the pantograph arms.The microscope will be employed to guide the work table relative. topositions marked on a drawing or similar 10- cating device 116 mountedon a table 118 supported from base 10.

However, as noted previously, themicroscope is only one means by whichthe work may be indexed with respect to a cutting tool, theplunger-template arrangement, previously described, providing anothermeans for accomplishing this purpose. In any event, however, thepantograph coupling is of the utmost importance in assuring not onlyaccuracy of location of the work, but also in implementing the ease ofmovement of the work relative to the cutting tool in the indexingoperation.

In locking the work table to the base, the application of vacuum will beemployed, as previously described. In many drilling and other machiningoperations it is frequently the practice to employ a cutting oil asa'cooling and lubricating fluid during the machining operations. Suchfluid in a device of the general character herein contemplated willordinarily be allowed to flow over the work table. As a result,application of the vacuum in locking the table to the base may cause thefluid to be sucked between the table and the base, and thence into thevacuum pump. This may create difficulty in operation of the equipmentand should be avoided, if possible. To

prevent this undesirable result when cooling fluid is used, the presentinvention contemplates a modification wherein the work table is providedwith an arrangement by which a current of air will be caused to blowdownwardly around the periphery of the work table and outwardlytherefrom so as to blow fluid falling on the surface of the base aboutthe work table away from the space between the work table and the basewhile the vacuum is being applied to lock the table to the base. Variousembodiments of such shield means may be employed.

As seen particularly in FIGS. 1, 2, and 7 to 9, the shield deviceincludes a frame 50, which may be constructed of metal, plastic, or anyother suitable strong material, which completely surrounds the peripheryof work table 11 and extends downwardly along the sides thereof to apoint generally flush with or slightly above the bottom face of worktable 11. The inner side of frame 50 is provided with a slot or groove51 which provides a clearance space between the frame and the side wallsof table 11 opening downwardly to the lower face of the table. A supplyof air under pressure is introduced into slot 51 from a suitable sourcethrough a fitting 52, generally simultaneously with the application ofvacuum between the work table and the base. The current of air will bedirected with suificient force and volume to blow strongly between theframe and the work table and against the upper surface of base 10, so asto form a barrier against inward flow of cooling fluid between the worktable and the base. In general, the arrows shown in FIGS. 1 and 2,indicate the outward direction of flow of the air which will prevent theentrance of liquid into the space between the worktable and the base.

FIG. 8 shOWs a modification very similar to FIG. 7, differing from thelatter in providing a somewhat greater space between the lower end offrame 50 and the upper surface of base 10, to more positively assureoutward flow of the air.

FIG. 9 illustrates still another modification wherein the shape of theslot in the frame is somewhat different from that in the earlierembodiments.

FIGS. 10 and 11 illustrate still other modifications in which a slot 53is formed in the lower face of work table 11 adjacent the peripherythereof and is supplied with air through passages 54, the air in thisarrangement being directed downwardly against the upper face of base 10and then outwardly between the work table and the base.

FIG. 11 is a slight modification of the slot form shown in FIG. 10, inthat the outer side wall of slot 53 is cut away to provide a somewhatgreater distance between the lower face of the outer edge of work table11 and the upper face of base 10 to assure the preferential discharge ofair outwardly of the work table.

As seen from the foregoing, the invention provides an improved apparatusfor positioning and looking a work piece preparatory to material removaland during such removal from the work piece. The apparatus for achievingthe positioning and locking includes a'source of gas pressure and atied-in vacuum source. Although gas, such as air, has provensatisfactory, it is evidentthat other gaseous fluids may be used in thepractice of the invention. The vacuum and the gas pressure are fedbetween the work table and the base, the gas pressure being used tofloat the work table for positioning thereof, and the vacuum thereuponbeing used to lock the work table to the base when located as desired,the vacuum source being used to lock the work table to the base as thefloating gas pressure is reduced to zero.

The present invention includes also the important arrangement foraccurately guiding the work table in indexing the same relative to thecutting tool, this arrangement being a pantograph-type coupling betweenthe work table and the base. The air barrier or shield for preventingentrance of liquid into the vacuum apparatus when using cooling fluidsand the like, constitutes still another high- 1y useful feature of anapparatus in accordance with this invention.

Although preferred embodiments of the invention have been shown anddescribed, it will be understood that numerous modifications andalterations may be made in the details of the illustrative embodimentswithin the scope of the appended claims but without departing from thespirit of this invention.

What I claim and desire to secure by Letters Patent is:

1. Apparatus for positioning a work piece, comprising (a) base meanshaving an upper planar bearing surace,

(b) a work-supporting table having a lower planar surface disposed formovement over said bearing surface,

(c) a source of gas pressure coupled to said base means to provide apneumatic bearing between said surfaces,

(d) a vacuum source coupled to said base means arranged to substitute avacuum for said gas pressure whereby to lock the work table to saidbearing surface solely by the force of said vacuum,

(e) indexing means operably disposed between the work table and the basemeans for indexing the work table on said bearing surface with respectto a cutting tool, and

(f) pantograph means operably connecting said work table to the basemeans to continuously maintain a true relation between the XY axes ofthe work table and said bearing surface throughout the indexingmovements of the work table.

2. Apparatus for positioning a work piece, comprising,

(a) base means having an upper planar bearing surface,

(b) a work-supporting table having a lower planar surface disposed formovement over said bearing surface,

(c) a source of gas pressure coupled to said base means to provide apneumatic bearing between said surfaces,

(d) a vacuum source coupled to said base means arranged to substitute avacuum for said gas pressure whereby to lock the work table to saidbearing surface solely by the force of said vacuum,

(e) indexing means operably disposed between the work table and the basemeans for indexing the work table on said bearing surface with respectto a cutting tool, and

(f) pantograph means operably connecting said work table to the basemeans to continuously maintain a true relation between the XY axes ofthe work table and said bearing surface throughout the indexingmovements of the work table,

(g) said pantograph means including a pivot ring, upper and lower pairsof parallel arms pivotally connecting said pivot ring respectively tosaid table and to said base means, at least one of said pairs of armsbeing of resilient construction to be bendable out of the plane of saidsurfaces.

3. In apparatus for positioning a work piece including,

(a) base means having an upper planar bearing surface,

(b) a work-supporting table having a lower planar surface disposed formovement over said bearing surface,

() a source of gas pressure coupled to said base means to provide apneumatic bearing between said surfaces, and

(d) a vacuum source coupled to said base means arranged to substitute avacuum for said gas pressure whereby to lock said table to said bearingsurface solely by the force of said vacuum,

(e) the improvement for blocking entrance of extra neous fluids betweensaid surfaces when said vacuum is applied, said improvement comprising,

(f) means carrier by said table aranged to direct a flow of pressurizedgas concentrically about the entire periphery of said table downwardlyagainst said bearing surface and outwardly of said periphery.

4. In apparatus for positioning a work piece including,

(a) base means having an upper planar bearing surface,

(-b) a work-supporting table having a lower planar surface disposed formovement over said bearing surface,

(c) a source of gas pressure coupled to said base means to provide apneumatic bearing between said surfaces, and

(d) a vacuum source coupled to said base means arranged to substitute avacuum for said gas pressure whereby to lock said table to said bearingsurface solely by the force of said vacuum,

(e) the improvement for blocking entrance of extraneous fluids betweensaid surfaces when said vacuum is applied, said improvement comprising,

(f) means carried by said table arranged to direct a flow of pressurizedgas concentrically about the entire periphery of said table downwardlytoward said surface and outwardly of said periphery,

(g) said last-mentioned means comprising downwardly opening narrowgroove means concentric with and closely adjacent the periphery of saidtable, and

(h) means for introducing pressurized gas into said groove means.

5. Apparatus for positioning a work piece, comprising,

(a) base means having an upper planar bearing surface,

(b) a work-supporting table having a lower planar surface disposed formovement over said bearing surface,

(0) a source of gas pressure coupled to said base means to provide apneumatic bearing between said surfaces,

(d) a vacuum source coupled to said base means arranged to substitute avacuum for said gas pressure whereby to lock the work table to saidbearing surface solely by the force of said vacuum,

(e) indexing means operably disposed between the work table and the basemeans for indexing the work table on said bearing surface with respectto a cutting tool,

(f) pantograph means operably connecting said work table to the basemeans to continuously maintain a true relation between the XY axes ofthe work table and said bearing surface throughout the indexingmovements of the work table, and

(g) means carried by said table arranged to direct a flow of pressurizedgas concentrically about the entire periphery of said table downwardlyagainst said bearing surface and outwardly of said periphery ReferencesCited UNITED STATES PATENTS 3,209,623 10/1965 Schardt 7764 FRANCIS S.HUSAR, Primary Examiner.

1. APPARATUS FOR POSITIONING A WORK PIECE, COMPRISING (A) BASE MEANSHAVING AN UPPER PLANAR BEARING SURFACE, (B) A WORK-SUPPORTING TABLEHAVING A LOWER PLANAR SURFACE DISPOSED FOR MOVEMENT OVER SAID BEARINGSURFACE, (C) A SOURCE OF GAS PRESSURE COUPLED TO SAID BASE MEANS TOPROVIDE A PNEUMATIC BEARING BETWEEN SAID SURFACES, (D) A VACUUM SOURCECOUPLED TO SAID BASE MEANS ARRANGED TO SUBSTITUTE A VACUUM FOR SAID GASPRESSURE WHEREBY TO LOCK THE WORK TABLE TO SAID BEARING SURFACE SOLELYBY THE FORCE OF SAID VACUUM, (E) INDEXING MEANS OPERABLY DISPOSEDBETWEEN THE WORK TABLE AND THE BASE MEANS FOR INDEXING THE WORK TABLE ONSAID BEARING SURFACE WITH RESPECT TO A CUTTING TOOL, AND (F) PANTOGRAPHMEANS OPERABLY CONNECTING SAID WORK TABLE TO THE BASE MEANS TOCONTINUOUSLY MAINTAIN A TRUE RELATION BETWEEN THE X-Y AXES OF THE WORKTABLE AND SAID BEARING SURFACE THROUGHOUT THE INDEXING MOVEMENTS OF THEWORK TABLE.